Synchronizing mechanism

ABSTRACT

A synchronizing mechanism provides a correlated seat-backrest movement of an office chair. To provide a self-adjusting synchronizing mechanism which is structurally simple, a backrest support is flexibly connected directly both to a base support so as to be pivotable about a transverse axis and to a seat support such that a pivoting movement of a backrest from an initial position into a rearwardly pivoted position induces an immediate lowering movement of the rear region of the seat support, when viewed in the longitudinal direction of the chair, rearwardly downward. The seat support is flexibly connected to the base support by a coupling element which is hinged to the seat support and to the base support such that when the backrest performs the pivoting movement from the initial position into the rearwardly pivoted position, an immediate lifting movement of the front region of the seat support, is effected rearwardly upward.

The invention relates to a synchronizing mechanism for a correlated seat-backrest movement of an office chair, having a base support which is placeable on a chair column, a seat support and a backrest support.

The term “synchronizing mechanism” is to be understood as assemblies in the seat substructure of an office chair which provide coupled-together kinematics which involve a certain relative movement of the seat and backrest with respect to one another. The seat of the office chair, which is generally provided with a padded seating area, is mounted on the seat support. The backrest support, which normally extends rearward from the actual synchronizing mechanism, carries the backrest of the office chair on an upwardly extending arm.

It is known to construct certain types of synchronizing mechanisms in such a manner that the user of the office chair is raised upward as a result of a load on the backrest itself. In other words, the user, when actuating the synchronizing mechanism, works by pushing the backrest back against his own weight resting on the seat. The desired pivoting resistance is consequently adjusted quasi automatically on account of the weight of the user.

The seat support and backrest support in the case of such self-adjusting synchronizing mechanisms are usually flexibly coupled in such a manner that a pivoting movement of the backrest toward the rear induces a lifting movement of both the rear and the front region of the seat such that the entire seat is raised, or, however, just the front region of the seat is raised whilst the height of the rear region of the seat is unalterable.

Such self-adjusting synchronizing mechanisms are often designed in a comparatively complex manner, consist of a plurality of interacting components and/or are costly and time-consuming to assemble.

An object of the present invention is to provide a self-adjusting synchronizing mechanism which is structurally particularly simple. Said object is achieved by a synchronizing mechanism according to claim 1. Advantageous realizations of the invention are provided in the sub-claims.

One idea of the invention is to reduce the number of coupling elements, in particular the number of elements connecting the seat support and the backrest support, in order, as a result, to achieve a particularly simple structural design of the mechanism without going without the desired functionality of a synchronizing mechanism. An idea of the invention over and above this is to provide a seat movement which deviates from the usual movement raising the seat where the so-called “shirt-riding-up effect” is nevertheless avoided. As a result, a particularly high level of seating comfort is achieved without having to resort to more costly and more time-consuming solutions.

This is achieved according to the invention as a result of the backrest support being flexibly connected directly, i.e. immediately and without any additional component connected in between, both to the base support so as to be pivotable about a transverse axis and consequently so as to define the main pivot axis of the mechanism, and to the seat support, in such a manner that a pivoting movement of the backrest from an initial position into a rearwardly pivoted position induces an immediate lowering movement of the rear region of the seat support, when viewed in the longitudinal direction of the chair, rearwardly downward and the seat support is flexibly connected to the base support by means of a coupling element which is hinged to the seat support and to the base support in such a manner that when the backrest performs the pivoting movement from the initial position into the rearwardly pivoted position, an immediate lifting movement of the front region of the seat support, when viewed in the longitudinal direction of the chair, is effected rearwardly upward.

In place of the otherwise usual raising of the entire seat, the rear region of the seat is therefore lowered into its rearwardly pivoted position when the backrest is pivoted, whilst the front region of the seat is raised. The lowering of the rear seat region, in this case, is effected directly each time the initial position is departed from without a lifting movement of the rear seat region being effected for instance first of all. In this case, the position in which the backrest is not rearwardly pivoted is deemed to be the initial position.

As a result of the seat support being lowered into its rearward region and at the same time the front region of the seat support being raised, the seat is entrained in a synchronous manner at a defined ratio to the backrest and a the seating area is inclined. As a result, the desired synchronous effect is produced where the angle of the seat support to the backrest support is changed.

The weight of the user directly affects the pivoting resistance which is noticeable by the user. A lighter user has to overcome a clearly smaller pivoting resistance when pivoting than a heavy user. Subjectively, the same “sensed” resistance is produced for each user when the backrest is pivoted.

As a result of the arrangement of the coupling elements and of the development thereof, the synchronous movement of the seat support can be individually adapted to the demands made on the chair. Thus, for example, as a result of changing the coupling lengths and/or angular positions, the degree of inclination of the seat support when the backrest pivots or the degree of displacement of the seat support toward the base support when the backrest pivots, when seen horizontally in the longitudinal direction of the chair, toward the rear, is adjustable.

The special synchronous movement of the mechanism according to the invention is preferably achieved in a particularly simple manner in that a coupling element, which is connected rigidly to the backrest support or is realized as an integral component part of the backrest support, is defined as a result of the positions of the hinging points of the backrest support on the base support, on the one hand, and on the seat support, on the other hand. In other words, a freely pivotable coupling element on both sides between the backrest support and the seat support is no longer necessary. Instead of which, the backrest support itself serves as a coupling element.

A particularly suitable coupling geometry and a synchronous movement resulting therefrom is achieved in a preferred embodiment of the invention as a result of the hinging point of the rear coupling element on the seat support, when viewed in the longitudinal direction of the seat, being located behind the hinging point of the rear coupling element on the base support in each position of the backrest support and the hinging point of the front coupling element on the seat support, when viewed in the longitudinal direction of the seat, being located in front of the hinging point of the front coupling element on the base support in each position of the backrest support. This is supported in an embodiment of the invention as a result of the front coupling element being connected to the seat support by means of a pure rotating joint and not, for instance, by means of a combined rotating/sliding joint.

Compared to other self-adjusting mechanisms, the present synchronizing mechanism is distinguished in that it is a particularly flat design such that a corresponding assembly only requires very little space. This also applies when for supporting or influencing the pivoting resistance and/or in order to prevent the backrest tipping uncontrollably toward the rear and for securely returning the backrest from the pivoted position into the initial position as soon as the user no longer loads the backrest, a spring mechanism with one or several spring elements is provided, as the spring mechanism can be realized in such a manner that the at least one spring element connects the base support to the backrest support without requiring further installation space over and above the housing volume of the base support provided in any case. This applies in particular when the spring element is connected to the front region of the base support and to the hinging point of the backrest support on the seat support and, as a result, is arranged in a comparatively flat manner in the interior of the assembly.

As the spring mechanism only acts in a supporting manner, the at least one spring element only needs to be realized in a comparatively weak manner such that all in all only small spring forces act on the components of the mechanism, which results in clearly reduced stress on the components compared to conventional mechanisms. In particular, no spring forces act on the seat support as this is moved exclusively by means of the backrest support. In other words, the seat support is entrained by the backrest support, more precisely by the coupling element of the backrest support which cooperates with the hinging point on the seat support, the transmission of the effective forces also being effected by means of said hinging point, whilst the coupling element which connects the seat support to the base support just has an action which co-controls the movement but does not transmit any force.

One embodiment of the invention has proved to be exceedingly advantageous where the spring mechanism comprises means for adjusting the preload of the at least one spring element, wherein the adjusting means include an adjusting handle which can be pulled out of the base support from a rest position incorporated in the base support into an actuating position for adjusting the preload. As a result, it is possible to operate the spring force adjusting means in a particularly elegant manner as once the desired preload has been adjusted, the adjusting handle can be pushed completely back into the base support again such that it closes off flush with the outside surface of the base support housing and does not cause any disturbance.

Such an adjustment handle is usable in a particularly good manner when the at least one spring element is a helical tension spring and the adjusting means include adjusting elements which are actuatable by means of the adjusting handle, by means of which the spacing between the spring ends of the helical tension spring is modifiable. In this case, the adjusting of the preload can be effected by rotating the adjustment handle about the longitudinal axis of the spring using simple adjusting elements. All in all, a means for adjusting the spring force which is realizable with few components and requires particularly little space is consequently produced.

Exemplary embodiments of the invention are explained below by way of the drawings, in which:

FIG. 1 shows a side view of the synchronizing mechanism in the initial position,

FIG. 2 shows a side view of the synchronizing mechanism in a maximum rearwardly pivoted position,

FIG. 3 shows a greatly abstracted representation of the interacting essential components of the synchronizing mechanism according to FIG. 1.

None of the Figures show the invention true to scale, they are purely schematic representations in this case and only show their essential component parts. The same references, in this case, correspond to elements with the same or comparable function. For better visibility, housing parts are sometimes not shown or are shown in a cut manner. Parts of spring elements are cut or not shown at all.

The synchronizing mechanism 100 comprises a base support 1 which is placed onto the top end of a chair column 10 by means of a tapered receiving means 2. Over and above this, the synchronizing mechanism 100 includes a substantially frame-shaped seat support 3 and a, in top view, fork-shaped backrest support 4, the cheeks 5 of which are arranged on both sides of the base support 1.

The seat support 3 is provided for receiving or mounting a preferably padded seating area (not shown). The mounting is effected in the usual manner by means of fastening elements which are not shown in any detail. A backrest, which is not shown in any detail and is height-adjustable in the case of modern office chairs, is mounted on the backrest support 4. The backrest can also be integrally connected to the backrest support 4.

The entire synchronizing mechanism 100 is constructed in a mirror-symmetrical manner with reference to its center longitudinal plane, which concerns the actual kinematics. In this respect, it must always be assumed in the following description that structural elements of the actual pivot mechanism are present in pairs on both sides.

FIGS. 1 and 3 show the initial position of the synchronizing mechanism 100 where the seat support 3 assumes a substantially horizontal position. FIG. 2 shows the synchronizing mechanism 100 with the backrest support 4 in a maximum rearwardly pivoted position.

In the rear region 6 of the seat, when viewed in the longitudinal direction 14 of the chair, the backrest support 4, which is pivotable in the pivot direction 7 about a transverse axis which defines the main pivot axis 11 of the synchronizing mechanism 100, is flexibly connected directly on the one side to the rear region 9 of the base support 1 and on the other side to the rear region 25 of the seat support 3. The backrest support 4, in this case, is hinged on the one side by means of a bearing pin to the base support 1 by way of the cheek 5 which extends in the direction of the seat front edge 8. The backrest support 4, in this case, is also flexibly connected directly to the seat support 3 on the other side, by way of a central entrainment arm 12 of the backrest support 4 which is arranged between the cheeks 5 of the backrest support 4 and extends obliquely upward in the direction of the base support 1.

The first joint axis 13, which is defined by the hinging of the backrest support 4 on the base support 1, when viewed in the longitudinal direction 14 of the chair, is arranged in front of the second joint axis 15 which is defined by the hinging of the backrest support 4 on the seat support 3. The second joint axis 15 is only slightly offset toward the rear in relation to the perpendicular on the main pivot axis of the synchronizing mechanism 100. A zenith position directly above the first joint axis 13 can, however, not be achieved. A pivoting of the backrest support 4 out of the initial position into a rearwardly pivoted position is consequently always linked with a lowering movement S of the rear region 25 of the seat support 3.

In the initial position, both joint axes 13, 15, when viewed in the longitudinal direction 14 of the chair, are situated in front of the center of the tapered receiving means 2. In the maximum rearwardly pivoted position, the second joint axis 15, when viewed in the longitudinal direction 14 of the chair, is situated behind the center of the tapered receiving means 2, whilst the position of the first joint axis 13 is unalterable in relation to the tapered receiving means 2.

A coupling element 16, which is connected rigidly to the backrest support 4 and is realized as an integral component part of the backrest support 4, is defined by the positions of the hinging points of the backrest support 4 on the base support 1 on the one side and on the seat support 3 on the other side, as is shown symbolically in FIG. 3 by way of the dot-dash line. The coupling element 16 is composed structurally from part of the cheeks 5, the central entrainment arm 12 and connecting elements which are not shown in any detail, but are also integral parts of the backrest support 4 and connect the cheeks 5 to the entrainment arm 12. The arrangement of the coupling element 16 directly above the tapered receiving means 2 contributes to an advantageous sequence of movement of the synchronizing mechanism 100.

The front region 18 of the base support 1 is flexibly connected to the front region 26 of the seat support 3 in the front region 17 of the seat. A coupling element 21, which is hinged on one side on the base support 1 and on the other side on the seat support 3, is provided for this purpose. The hinging point of the coupling element 21 on the base support 1 and consequently the third joint axis 22 is situated, when viewed in the longitudinal direction 14 of the chair, behind the hinging point of the coupling element 21 on the seat support 3 and consequently behind the fourth joint axis 23.

The sequence of the arrangement of the joint axes 13, 15, 22, 23 does not change even when the synchronizing mechanism 100 is in a maximum rearwardly pivoted position. The rear coupling element 16, when viewed in the longitudinal direction 14 of the chair, points in each case obliquely upward and rearward and the front coupling element 21, when viewed in the longitudinal direction 14 of the chair, points in each case obliquely upward and forward. In this case, the joint axes 15, 23 at the hinging points of the seat support 3, when viewed in the vertical direction, always extend above the joint axes 13, 22, which are defined by the hinging on the base support 1. The coupling elements 16, 21 are arranged in a V-shaped manner with respect to one another, the imaginary extension lines of the coupling elements 16, 21 intersecting below the base support 1. The relative movement of the seat support 3 and the backrest support 4 with respect to one another is determined by the position of the total of four joint axes 13, 15, 22, 23 which extend through the ends of the two coupling elements 16, 21 and are defined by the hinging points.

The pivoting mechanism described ensures that the backrest support 4 can be pivoted with the backrest in the pivot direction 7 about the main pivot axis 11, here the first joint axis 13. At the same time, the rearward pivoting movement of the backrest induces an immediate lowering movement S of the rear region 25 of the seat support 3 rearwardly downward and the front region 26 of the seat support 3 completes a lifting movement H rearwardly upward. When the backrest pivots, the seat support 3 is at the same time displaced rearward, whilst the base support 1 with the pivot bearings 13, 22 remains fixed in position.

A realization with the following development has proved particularly advantageous for a synchronizing movement which supports the intuitive human sequence of movement when pivoting rearward and at the same time avoids the shirt-riding-up effect:

The acute angle 27 enclosed between the rear coupling element 16 and the horizontal in the non-pivoted initial position is preferably between 1.5 and 1.8 times, in a particularly preferred manner between 1.6 and 1.7 times the acute angle 28 enclosed between the front coupling element 21 and the horizontal. In the example shown, the angle 27 in the case of the rear coupling element 16 is approximately 85° and the angle 28 in the case of the front coupling element 21 is approximately 52°.

In the maximum rearwardly pivoted position, the backrest support 4 is pivoted rearwardly downward preferably by between 20° and 25°, in a particularly advantageous manner rearwardly downward by between 22° and 24°. In the example shown, said angle is 23° in relation to the initial position. The inclination of the seat support 3 to the horizontal initial position in this case is preferably between 6° and 9°, in a particularly preferred manner between 7° and 8°. In the example shown, the inclination is approximately 7.3°.

In the maximum rearwardly pivoted position, the acute angle 28 enclosed between the front coupling element 21 and the horizontal is preferably between 1.1 and 1.3 times, in a particularly preferred manner approximately 1.2 times the acute angle 27 enclosed between the rear coupling element 16 and the horizontal. In the example shown, the angle 28 in the case of the front coupling element 21 is approximately 74° and the angle 27 in the case of the rear coupling element 16 is approximately 62°.

The effective length of the rear coupling element 16, which is defined by the pivot points and consequently the position of the joint axes 13, 15, is preferably between 1.1 and 1.3 times, in a particularly preferred manner approximately

1.2 times the effective length of the front coupling element 21, which is defined by the position of the joint axes 22, 23. In the example shown, the effective length of the rear coupling element 16 is approximately 60 mm and the effective length of the front coupling element 21 is approximately 70 mm.

A spring arrangement with a centrally arranged spring element is provided to influence the pivoting resistance. In this case, this is a helical tension spring 30 which is arranged in a sloping manner in the base support 1 and is supported on one side on the front region 18 of the base support 1 and on the other side on the backrest support 4, more precisely on the entrainment arm 12 of the backrest support 4, and which is loaded when the backrest support 4 is pivoted rearwardly downward.

The spring 30 is supported with its fixed end, which points forward in the longitudinal direction 14 of the chair, on a front thrust bearing 31 and with its oppositely situated moveable end on a spring cup 32. A guide rod 33 which is encompassed by the spring 30 is connected to the spring cup 32. A threaded spindle 35, which is connected to an adjusting handle 34, is provided in the interior of the guide rod 33. In this case, the adjusting handle 34 and the threaded spindle 35 are connected together in a suitable manner such that a rotation of the adjusting handle 34 about a rotational axis 36, which corresponds to the longitudinal axis of the spring and the spindle axis, brings about a rotation of the rotary spindle 35 when the adjusting handle 34 is pulled out of its rest position incorporated in the housing 20 of the base support 1 into an actuating position (not shown) and is rotated in said position.

The front thrust bearing 31 is suspended in the housing 20 of the base support 1. The threaded spindle 35 is mounted so as to be rotatable in a rear thrust bearing 27 which is fixed in position in relation to the threaded spindle 35. The rear thrust bearing 37 is flexibly connected to the entrainment arm 12 in a suitable manner in the region of the second joint axis 15 such that it is entrained when the backrest support 4 is pivoted. The spring 30, in this case, is preferably arranged in such a manner and the connection between the spring 30 and the backrest support 4 is preferably realized in such a manner that in the initial position the effective line of the spring 30 is substantially perpendicular to a line between the hinging point 13 of the backrest support 4 on the base support 1 and the application point of the spring 30 on the backrest support 4.

To adjust the preload of the spring 30, the adjusting handle 34 is pulled out into its actuating position and rotated. As a result of the rotation of the threaded spindle 35 that this causes, the rear thrust bearing 37, which is operatively connected to the spring cup 32, brings about a change in the spacing between the spring ends and consequently a change in the preload. To reduce the preload, the threaded spindle 35 is rotated in such a manner that the spring cup 32, which is mounted so as to be movable on the threaded spindle 35, acted upon by the thrust bearing 37, is moved in the direction of the front thrust bearing 31. To increase the preload, the threaded spindle 35 is rotated in such a manner that the spring cup 32 on the threaded spindle 35 is moved rearward. The adjusting handle 34 is then pushed back again into its rest position in the housing 20 of the base support 1.

All the features shown in the description, the following claims and the drawing can be essential to the invention both individually and together in arbitrary combination.

LIST OF REFERENCES

1 Base support

2 Tapered receiving means

3 Seat support

4 Backrest support

5 Cheek

6 Rear seat region

7 Pivot direction

8 Seat front edge

9 Rear region of the base support

10 Chair column

11 Main pivot axis

12 Entrainment arm

13 First joint axis

14 Longitudinal direction of the chair

15 Second joint axis

16 Rear coupling element

17 Front seat region

18 Front region of the base support

19 (blank)

20 Housing of the base support

21 Front coupling element

22 Third joint axis

23 Fourth joint axis

24 (blank)

25 Rear region of the seat support

26 Front region of the seat support

27 Angle

28 Angle

29 (blank)

30 Helical tension spring

31 Front thrust bearing

32 Spring cup

33 Guide rod

34 Adjusting handle

35 Threaded spindle

36 Rotational axis

37 Rear thrust bearing

100 Synchronizing mechanism

H Lifting movement

S Lowering movement 

1-10. (canceled)
 11. A synchronizing mechanism for a correlated seat-backrest movement of an office chair, the synchronizing mechanism comprising: a base support for placing on a chair column of the office chair; a seat support having a front region and a rear region for supporting a seat of the office chair; a backrest support for supporting a backrest of the office chair, said backrest support being flexibly connected directly both to said base support so as to be pivotable about a transverse axis and to said seat support such that a pivoting movement of the backrest from an initial position into a rearwardly pivoted position induces an immediate lowering movement of said rear region of said seat support, when viewed in a longitudinal direction of the office chair, rearwardly downward; a front coupling element, said seat support being flexibly connected to said base support by said front coupling element, said front coupling element being hinged to said seat support and to said base support such that when the backrest performs the pivoting movement from the initial position into the rearwardly pivoted position, an immediate lifting movement of said front region of said seat support, when viewed in the longitudinal direction, is effected rearwardly upward; and a spring mechanism for adjusting a pivoting resistance of the backrest, said spring mechanism containing at least one spring element connecting said base support to said backrest support.
 12. The synchronizing mechanism according to claim 11, further comprising a rear coupling element, which is connected rigidly to said backrest support or is realized as an integral component part of said backrest support, and is defined as a result of positions of first and second hinging points of said backrest support on said base support, said rear coupling element rigidly connected also to said seat support, at least one of a position or a length of said rear coupling element, with consideration to a position and/or a length of said front coupling element which is disposed between said seat support and said base support, influences the correlated seat-backrest movement to be achieved.
 13. The synchronizing mechanism according to claim 12, wherein the first hinging point of said rear coupling element on said seat support, when viewed in the longitudinal direction of the seat, lies behind the second hinging point of said rear coupling element on said base support in each position of said backrest support.
 14. The synchronizing mechanism according to claim 12, wherein a first hinging point of said front coupling element on said seat support, when viewed in the longitudinal direction of the seat, lies in front of a second hinging point of said front coupling element on said base support in each position of said backrest support.
 15. The synchronizing mechanism according to claim 12, further comprising a pure rotating joint, said front coupling element is connected to said seat support by means of said pure rotating joint.
 16. The synchronizing mechanism according to claim 11, wherein said spring element is connected to said base support as well as to said backrest support.
 17. The synchronizing mechanism according to claim 16, wherein said spring element is disposed in such a manner that an effective line of said spring element in a non-pivoted initial position is substantially perpendicular to a line which connects a hinging point of said backrest support on said base support to a point of application of said spring element on said backrest support.
 18. The synchronizing mechanism according to claim 11, wherein said spring mechanism contains adjusting means for adjusting a preload of said at least one spring element, wherein said adjusting means include an adjusting handle which can be pulled out of said base support from a rest position incorporated in said base support into an actuating position for adjusting the preload.
 19. The synchronizing mechanism according to claim 18, wherein said at least one spring element is a helical tension spring and said adjusting means include adjusting elements which are actuatable by means of said adjusting handle and by means of which a spacing between spring ends of said helical tension spring is modifiable.
 20. The synchronizing mechanism according to claim 11, wherein said spring element is connected to said a front region of said base support as well as to a hinging point of said backrest support on said seat support or in a direct vicinity of the hinging point. 